KEY DIFFERENCE. C is a Procedural Oriented language, whereas C++ is an Object-Oriented Programming language. C does not allow you to use function overloading whereas C++ allows you to use function overloading. C supports built-in data types whereas C++ supports built-in as well as user-defined data types.
C# is an object-oriented programming language used with XML-based Web services on the . ... C# boasts type-safety, garbage collection, simplified type declarations, versioning and scalability support, and other features that make developing solutions faster and easier, especially for COM+ and Web services.